The desirability of humidifying or adding moisture to lint cotton in the cotton gin just before baling has been recognized for years. Although humidifying lint cotton increases the weight of the cotton, there are also many significant advantages to adding moisture at this stage of cotton processing. Adding moisture to lint cotton improves the capacity of the bale press whereas dry cotton requires higher compression forces and more time to charge and compact it into the press box. Dry cotton is also more difficult to press into a bale than cotton of normal moisture content. Higher press box compaction pressures require more bale press energy consumption, which causes wear and tear on the bale press components. Thus, humidified lint requires lower compaction pressures and reduces strain on the bale press components while creating bales that are within the acceptable weight range. Adding moisture to the fiber and compressing the batt before the press also enhances the press capacity since a denser volume of cotton is available for each charge of cotton delivered to the press box.
Older cotton presses use troublesome devices known as "dogs" to hold the compacted cotton in the press box while additional cotton is being added to form the bale. Modern high capacity, universal density presses do not use dogs. However, without dogs to hold the cotton in the box during bale formation, dry cotton springs out of the box requiring the tramper to work harder as it recompacts the cotton. In contrast, humidified lint stays in the box after compaction.
Bands consisting of wires or straps of steel are used to hold the formed bale together after the bale pressing operation. Dry cotton requires additional force to press it into a bale. The additional force causes excessive tension on the bands, thereby causing some of the bands to break during bale storage. Replacing broken bands is an expensive process for the warehouse. The rebanding process can also lead to contamination of the lint fiber which lowers the value of the cotton. Adding moisture to the cotton before the baling process reduces the occurrence of broken bands.
Several prior art methods have had limited success in humidifying lint cotton. Spraying the cotton batt with a fine mist of water to which a wetting agent had been added was probably the first systematic way used to apply moisture to lint cotton. This method was developed by the U.S. Government's Cotton Ginning Laboratory, at Stoneville, Miss., and was described by Charles A. Bennett in his article "Engineering Progress in Cotton Ginning" which appeared in the Cotton Gin and Oil Mill Press on Mar. 22, 1947. The apparatus employing this method is described in U.S. Pat. No. 3,324,513, issued Jun. 13, 1967, to D. B. Hurdt.
Exposing cotton to a stream of warm, humid air is the most popular method of humidifying cotton at the gin. Typically, the warm, humid air is generated by a device manufactured by Samuel Jackson, Inc., under the trademark HUMIDAIRE and controlled by the applicant herein. This device comprises an air heater in which a gas or oil-fired burner operates with an open flame in the stream of air to be humidified. The stream of air passes through an air washer chamber in which recirculated water spray scrubs the heated air, simultaneously cooling the air and evaporating the water. A supply of warm humid air is generated with an air temperature between 120 to 160 degrees F. dry-bulb temperature and 70 to 100% relative humidity.
The relative humidity of the air generated by the HUMIDAIRE device is regulated by independent control of the dry-bulb (air) and wet-bulb (water) temperatures. The closer these two temperatures are together, the higher the relative humidity. Regulating the burner fuel valve controls the dry-bulb temperature. Regulating the butterfly valve for throttling water flow to the spray nozzles in the air washer chamber controls the wet-bulb temperature.
At present, the most common lint cotton humidifier is the "Lint Slide Grid Humidifier," U.S. Pat. No. 4,103,397, issued Aug. 1, 1978, to S. G. Jackson. This device comprises a set of louver-like plates, or grids, forming the bottom surface of the lint slide between the battery condenser and press. Humid air is introduced in a plenum below the grids and passes up through the grids and through the cotton batt flowing downward to the press. Although this device offers a low cost solution, it is only capable of applying a limited amount of humid air to the cotton. The effectiveness of this device is limited since some of the air escapes around the cotton batt instead of penetrating it. In addition, this device is incapable of compressing the batt into a desirable denser mass.
An alternative location for applying humid air to the cotton batt is at the battery condenser of the gin. Humid air may be applied just before cotton reaches the doffing rollers of the screen drum of the battery condenser. For an example of this method, see U.S. Pat. No. 2,834,058, issued May 13, 1958, to W. R. Bryant. This humidification method has disadvantages. Since the humid air must pass through the screen drum of the condenser, moisture will often condense on the screen drum in cold weather, thereby causing the screen drum to "hair over" with cotton fibers that cannot be removed by the doffing rollers Air blockages result and the device soon chokes, resulting in downtime.
Before the introduction of the humidifier of U.S. Pat. No. 4,103,397, warm humid air was injected into the air and lint flowing to the battery condenser. A limited amount of lint humidification could be achieved this way. However, applying enough humid air to affect the moisture of the lint usually resulted in moisture condensing on the cold battery condenser screen, thus hairing the screen over as described before.
U.S. Pat. No. 4,140,503, issued Feb. 20, 1979, to A. L. Vandergriff, describes a method of applying dry, heated air to the condenser screen drum after the doffer rollers to attempt to dry the condensation off the screen. This patent also describes an arrangement of rollers for receiving the humidified cotton batt from the doffing rollers and compressing the cotton batt. The batt leaves the rollers and begins the descent down the slide to the press. Unfortunately, this device retains the inherent problem of moisture condensation on the screen and rollers since it applies moisture in the battery condenser.